Knee osteoarthritis (OA) is symptomatic in 12.1% of Americans over 60 years of age. The patellofemoral joint is involved in 50% of all radiographic knee osteoarthritis cases in either an isolated form or combined with tibiofemoral OA. Despite the prevalence of patellofemoral OA, the patellofemoral joint has received relatively little attention in the OA literature and there are few treatment options for individuals with patellofemoral OA.
The patella rests in a groove at the distal end of the femur called the trochlear groove. When the knee is extended and flexed, the patella tracks superiorly and inferiorly, respectively, inside the groove. Both the posterior aspect of the patella and the trochlear groove are covered with articular cartilage that allows the bones to glide smoothly along each other as the leg is flexed and extended.
Patellofemoral arthritis occurs when the articular cartilage lining the trochlear groove and on the posterior aspect of the patella deteriorates and becomes inflamed. The joint space in the knee is narrowed due to the patellofemoral arthritis. Additionally, bone spurs may develop due to the arthritis in the knee.
As the articular cartilage deteriorates it becomes frayed, and when the wear is severe, the underlying bone may become exposed. Moving the bones along this rough surface generates friction and can be painful. Overload osteoarthritis, a condition that resembles osteoarthritis in any other joint, i.e., a gradually progressive thinning of the cartilage related to “normal wear and tear” that in this case is restricted to, or starts in, the patellofemoral compartment of the knee, may also occur.
In additional to patellofemoral arthritis, patellofemoral pain may also be the result of patellofemoral pain syndrome, patellar tendonitis, chondromalacia, and patella maltracking.
There are numerous devices that have been developed and marketed to help alleviate patellofemoral pain. The currently available devices generally either attempt to adjust the patella position and movement by pushing it inward (posteriorly) and/or medially or laterally. Some devices attempt to reduce the load on the patella by distributing the forces either above and/or below the knee joint and away from the patella region. However, a study disclosed in McWalter, et al., “The Effect of Patellar Brace on Three-Dimensional Patellar Kinematics in Patients with Lateral Patellofemoral Osteoarthritis,” Osteoarthritis Cartilage 19(7):801-808 (2011) concluded that while bracing changed patellar kinematics, the changes in kinematics did not provide a clinically meaningful reduction in pain in the study. Therefore, a need still exists for a device that can effectively manage patellofemoral joint pain and inflammation.
The present invention is directed to overcoming these and other deficiencies in the art.